1. Field of the Invention
The present invention relates to an imaging apparatus that performs wireless communication with a light emitting apparatus by using radio waves.
2. Description of the Related Art
Conventionally, there has been known a camera system that performs flash photography by using a camera and a flash apparatus disposed remotely from the camera. Japanese Patent Application Laid-Open No. 2000-89306 discusses a technique for transmitting a light pulse signal by a camera to a flash apparatus to control the flash apparatus.
Further, for example, Japanese Patent Application Laid-Open No. 05-127215 discusses a technique for calculating an amount of main light emission of a flash apparatus based on a light metering value when the flash apparatus performs preliminary light emission and a light metering value when the flash apparatus emits no light to achieve excellent flash photography. However, if the camera system discussed in Japanese Patent Application Laid-Open No. 2000-89306 calculates an amount of main light emission of the flash apparatus disposed remotely from the camera according to the method discussed in Japanese Patent Application Laid-Open No. 05-127215, a following problem arises.
FIG. 6 illustrates timing of each operation from an issuance of an imaging start instruction from a user to an actual start of an imaging operation, in a camera system that performs flash photography by using a camera and a flash apparatus disposed remotely from the camera. In particular, in the system illustrated in FIG. 6, a flash apparatus mounted on the camera (hereinafter referred to as “master flash apparatus”) transmits a light signal to the flash apparatus disposed remotely from the camera (hereinafter referred to as “slave flash apparatus”).
In calculating a main light emission amount of the slave flash apparatus according to the method discussed in Japanese Patent Application Laid-Open No. 05-127215, the operations are performed in the following order.
First, the camera meters light when the slave flash apparatus emits no light to acquire a light metering value at the time of no light emission. Then, the master flash apparatus transmits a light signal of preliminary light emission to the slave flash apparatus, so as to cause the slave flash apparatus to perform preliminary light emission. Then, upon receiving the light signal of preliminary light emission, the slave flash apparatus performs preliminary light emission, and the camera meters light in synchronization with the preliminary light emission of the slave flash apparatus, thereby acquiring a light metering value at the time of preliminary light emission.
The camera calculates an amount of main light emission of the slave flash apparatus based on the light metering value at the time of no light emission, and the light metering value at the time of preliminary light emission acquired in the above-mentioned manner.
After the calculation of a main light emission amount of the slave flash apparatus, the camera transmits a light signal indicating information related to main light emission of the slave flash apparatus (an amount of main light emission, timing of main light emission, and duration of main light emission) via the master flash apparatus. Further, the camera transmits a light signal instructing main light emission, and captures an image in synchronization with the main light emission of the slave flash apparatus.
As understood from the above description, if a camera calculates an amount of main light emission of a slave flash apparatus and then captures an image while causing the slave flash apparatus to emit light according to the method discussed in Japanese Patent Application Laid-Open No. 05-127215, the camera should transmit, for example, an instruction for preliminary light emission and information about main light emission to the slave flash apparatus. Further, a camera system including a plurality of slave flash apparatuses should perform the above-described processing regarding calculation of a main light emission amount for each of the slave flash apparatuses.
However, a camera cannot transmit, for example, an instruction for preliminary light emission and information about main light emission to a slave flash apparatus while metering light, since such an instruction and information are transmitted in the form of a light signal.
Therefore, if a camera calculates an amount of main light emission of a slave flash apparatus and then captures an image while causing the slave flash apparatus to emit light according to the method discussed in Japanese Patent Application Laid-Open No. 05-127215, a delay time from an issuance of an imaging start instruction to an actual start of an imaging operation becomes longer, compared to a camera that captures an image while causing only a master flash apparatus to emit light.